[clang][modules] Detect invalidation of SDKSettings.json

clang/lib/Index/IndexingAction.cpp

@@ -919,6 +919,8 @@ class ModuleFileIndexDependencyCollector : public IndexDependencyProvider {
           // undesirable dependency on an intermediate build byproduct.
           if (FE->getName().ends_with("module.modulemap"))
             return;
+          if (FE->getName().ends_with("SDKSettings.json"))
+            return;
 
           visitor(*FE, isSystem);
         });

clang/lib/Serialization/ASTWriter.cpp

@@ -5950,6 +5950,18 @@ ASTFileSignature ASTWriter::WriteASTCore(Sema *SemaPtr, StringRef isysroot,
   if (Chain)
     Chain->finalizeForWriting();
 
+  // FIXME: This is here because the include-tree file list refers to this file
+  // and we need to validate it's up-to-date when reading the AST file. Make
+  // this more generic and include the remaining files.
+  StringRef Sysroot = PP->getHeaderSearchInfo().getHeaderSearchOpts().Sysroot;
+  if (!Sysroot.empty()) {
+    SmallString<128> SDKSettingsJSON = Sysroot;
+    llvm::sys::path::append(SDKSettingsJSON, "SDKSettings.json");
+    if (auto FE = PP->getFileManager().getOptionalFileRef(SDKSettingsJSON))
+      PP->getSourceManager().createFileID(*FE, SourceLocation(),
+                                          SrcMgr::C_System);
+  }
+
   // This needs to be done very early, since everything that writes
   // SourceLocations or FileIDs depends on it.
   computeNonAffectingInputFiles();

clang/test/ClangScanDeps/modules-include-tree-sdk-settings.c

@@ -0,0 +1,37 @@
+// This test checks that the module cache gets invalidated when the
+// SDKSettings.json file changes. This prevents "file changed during build"
+// errors when the TU does get rescanned and recompiled.
+
+// REQUIRES: ondisk_cas
+
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+//--- sdk/SDKSettings.json
+{
+  "Version": "11.0",
+  "MaximumDeploymentTarget": "11.0.99"
+}
+
+//--- module.modulemap
+module M { header "M.h" }
+//--- M.h
+//--- tu.c
+#include "M.h"
+
+// RUN: clang-scan-deps -format experimental-include-tree-full -cas-path %t/cas -o %t/deps_clean.json \
+// RUN:   -- %clang -target x86_64-apple-macos11 -isysroot %t/sdk \
+// RUN:      -c %t/tu.c -o %t/tu.o -fmodules -fmodules-cache-path=%t/cache
+
+// RUN: sleep 1
+// RUN: echo " " >> %t/sdk/SDKSettings.json
+// RUN: echo " " >> %t/tu.c
+
+// RUN: clang-scan-deps -format experimental-include-tree-full -cas-path %t/cas -o %t/deps_incremental.json \
+// RUN:   -- %clang -target x86_64-apple-macos11 -isysroot %t/sdk \
+// RUN:      -c %t/tu.c -o %t/tu.o -fmodules -fmodules-cache-path=%t/cache
+
+// RUN: %deps-to-rsp %t/deps_incremental.json --module-name M > %t/M.rsp
+// RUN: %deps-to-rsp %t/deps_incremental.json --tu-index 0 > %t/tu.rsp
+// RUN: %clang @%t/M.rsp
+// RUN: %clang @%t/tu.rsp

clang/tools/c-index-test/core_main.cpp

@@ -861,7 +861,8 @@ static int scanDeps(ArrayRef<const char *> Args, std::string WorkingDirectory,
         llvm::outs() << "      " << ModuleName << "\n";
       llvm::outs() << "    file-deps:\n";
       for (const auto &FileName : ArrayRef(FileDeps.Strings, FileDeps.Count))
-        llvm::outs() << "      " << FileName << "\n";
+        if (!StringRef(FileName).ends_with("SDKSettings.json"))
+          llvm::outs() << "      " << FileName << "\n";
       llvm::outs() << "    build-args:";
       for (const auto &Arg :
            ArrayRef(BuildArguments.Strings, BuildArguments.Count))

clang/tools/clang-scan-deps/ClangScanDeps.cpp

@@ -601,7 +601,8 @@ template <typename Container>
 static auto toJSONStrings(llvm::json::OStream &JOS, Container &&Strings) {
   return [&JOS, Strings = std::forward<Container>(Strings)] {
     for (StringRef Str : Strings)
-      JOS.value(Str);
+      if (!Str.ends_with("SDKSettings.json"))
+        JOS.value(Str);
   };
 }
 
@@ -764,7 +765,10 @@ class FullDeps {
                                toJSONStrings(JOS, MD.getBuildArguments()));
             JOS.attribute("context-hash", StringRef(MD.ID.ContextHash));
             JOS.attributeArray("file-deps", [&] {
-              MD.forEachFileDep([&](StringRef FileDep) { JOS.value(FileDep); });
+              MD.forEachFileDep([&](StringRef FileDep) {
+                if (!FileDep.ends_with("SDKSettings.json"))
+                  JOS.value(FileDep);
+              });
             });
             JOS.attributeArray("link-libraries",
                                toJSONSorted(JOS, MD.LinkLibraries));